Process for producing the disodium salt of imidodicarboxylic acid



Patented Jan. 5, 1937 PATENT OFFICE 7 2,067,013 PROCESS ronrnonocmo THE DISODI"UM i SALT OF IMIDODICARBOXYLIO ACID Robert B. Mat /mum, Niagara Falls, N. Y.', to The: Mathieson Alkali Works,"l'ri Signor New York, N; Y., a corporation of Virginia No'Drawingi Application octoiier 2, 1935,

Serial No. 43,178

3 Claims. (Cl. 260-112) My invention relates tothe production of the compound having the formula:

Na-O-C which is hereinafter referred to as-disodium imidodicarboxylate. More particularly my invention relates to the production of disodium imidodicarboxylate by heating I sodium carbamate.

' 'lhis applicationis in part a continuationof my prior co-pending application, Serial No. 607,510, filed April 25, 1932.

It has been proposed to prepare disodium imidodicarboxylate by heating sodium carbamate at temperatures of 200 C. and upwards. I have discovered, however, that disodium imidodicarboxylate can be prepared by heating dry sodium carbamate in a dry atmosphere at temperatures below 200 C. Temperatures of 100-190 C. may be used in carrying out the process of my invention.

Temperatures of l-150 C. are advantageous, a temperature of 140-150 C. being particularly advantageous.

While conversion'of sodium carbamate to disodium imidodicarboxylate can be effected at temperatures of 200 C. and upwards, several advantages are tobe obtained by carrying out the conversion according to the process of my invention. Disodium imidodicarboxylate is stable at temperatures up to 200 C., but at temperatures of about 200 C. it decomposes to form sodium carbonate and sodium cyanate. The use of temperatures of 200 C. and upwards involves danger of decomposition of the desired product, requiring critical control of reaction conditions to avoid excess decomposition. Again, maximum dissociation of the sodium carbamate to disodium imidodicarboxylate takes place at a temperature of 140-l50 C. It will thus be seen that the process of my invention affords advantages both with respect to the extent of conversion of sodium carbamate to disodium imidodicarboxylate and decomposition of the formed product. Further, theseadvantages are obtained while requiring less critical control of the reaction conditions, an important advantage in itself.

When dry sodium carbamate, NaCOzNHz, is heated to the temperatures employed in the process of my invention in a dry atmosphere, onehalf of the nitrogen is evolved as ammonia to the i substantial exclusion of carbon dioxide and water vapor, as follows:

The heating may be carried out under atmos pheric pressure, sub-atmospheric pressures or' pressures somewhat higher than atmospheric" pressure. The compound so produced, disodium imidodicarboxylate, isa solid, stable at temperatures up to 200 C., and is less hygroscopic than. sodium carbamate. It has valuable detergent'and anti-acid properties. It is an advantageous household cleanser. It hydrolyzes, in water, to sodium bicarbonate and ammonium hydroxide,

' as follows:

illustrate the effect of heat on sodium carbamate:

TABLE I Vapor pressure NaCOaNHr Temp. 0. Dynamic Static Pun oo, P P

90, 87.2 mm. 69.3 146.5 161.3 135-140 About 710 From the above table it will be apparent that the dissociation temperature of the sodium carbamate is just slightly above 140 0., because at the temperature of 140 C. the pressure had nearly approximated that of the atmosphere.

TABLE II Efiect of heating NaCOzNHz underNHs pressure Note: Original PNH3=100 lb/sq. in. gauge Max. Time I temp. $23 NaooiNn,

f in. (hrs) 100' 100' 21a 19 100 400 5' I o 550 4 0 s00 s 0 Per cent 09 Ndas (NaoomNH N32010: NaQNO NaC N 0 o o o o o o 0 1s 13 14 0 as 51 1s 0 o 77 21 2 From Table I it will be seen that sodium carbamate dissociates at about 145 C. when heated even in the absence of air to give off ammonia and some carbon dioxide. The higher the temperature the greater will be the proportion of amm'onia to carbon dioxide. Table II shows the results of heating sodium carbamate under an original NH3 pressure of 100 lbs/sq. in. gauge. From the table it is seen that sodium carbamate undergoes no change upon being heated to C. but that its dissociation to form (NaCOz) zNH has passed its peak at l50-180 C. In the last example of Table II fusion of the mixture occurred.

My invention will now be illustrated in connecbamate to a temperature of 140-150 tion with the following example but it will be understood that the example is merely illustrative of the invention and not limiting:

Example I parts of sodium carbamate consisting of 84.6% (by weight) NaCOzNHz, 8.5% NaHCOz and 6.9% H20 are spread in a thin layer on the trays of a drying cabinet or other suitable apparatus,

- the temperature of which can be controlled, and

heated to a temperature of C. for approximately one hour while circulating dry air over the material. The ammonia given off into the circulating air may be removed and recovered by absorption in Water, for example. 81.4 parts of a product'containing approximately 93% dlsodium imidodicarboxylate are obtained.

. .The presence of moisture is undesirable as it 1 bamate to a temperature at which nitrogen is evolved as ammonia not exceeding C. in a dry atmosphere.

2. A process for producing dlsodium imidodicarboxylate comprising heating dry sodium carbamate to a temperature of 100-190 C. in a dry atmosphere. p v

3. A process for producing disodium imidodicarboxylate comprising heating dry sodium car- C. in a dry atmosphere.

-1 ROBERT E. MACMULLIN. 

